u/tempicide

I've got four points of data and I know the pattern that would create the next points, but I'm trying to remember the process for turning it into a properly written out function. I haven't had a math class in eleven years and I just want to remember how this works lol.

So the four points I have are at (1, 90), (2, 50), (3, 30), and (4, 20). The pattern is that each y value is half of the previous y value plus 5. Remind me of the process to figure out the function that creates this graph? I am so far detached from algebra due to non use that I don't even remember where to begin, I've been spitballing ideas around and I've at least recognized that there's a power of x greater than one involved as well as an inverse function, right? But then, a power greater than one would mean the value of y would begin to grow eventually and it never does from what I can see, it has an asymptote close to y = 10

My new gig allows hands free calls while driving, but I'm not to touch my phone even to so much as hang up. I have been using a pair of Sennheisers that I've had for years instead of a proper headset, but the company doesn't want me using it because neither ear is detachable. I am on an uber tight budget right now, so I need the cheapest possible option for a headset that is wireless, has a button to answer and hang up calls, and has one ear only or a detachable ear. What can you guys recommend?